Imaging Optimization in Children

Hierarchical Perception Adversarial Learning Framework for Compressed Sensing MRI

The long acquisition time has limited the accessibility of magnetic resonance imaging (MRI) because it leads to patient discomfort and motion artifacts. Although several MRI techniques have been proposed to reduce the acquisition time, compressed sensing in magnetic resonance imaging (CS-MRI) enables fast acquisition without compromising SNR and resolution. However, existing CS-MRI methods suffer from the challenge of aliasing artifacts. This challenge results in the noise-like textures and missing the fine details, thus leading to unsatisfactory reconstruction performance. To tackle this challenge, we propose a hierarchical perception adversarial learning framework (HP-ALF). HP-ALF can perceive the image information in the hierarchical mechanism: image-level perception and patch-level perception. The former can reduce the visual perception difference in the entire image, and thus achieve aliasing artifact removal. The latter can reduce this difference in the regions of the image, and thus recover fine details. Specifically, HP-ALF achieves the hierarchical mechanism by utilizing multilevel perspective discrimination. This discrimination can provide the information from two perspectives (overall and regional) for adversarial learning. It also utilizes a global and local coherent discriminator to provide structure information to the generator during training. In addition, HP-ALF contains a context-aware learning block to effectively exploit the slice information between individual images for better reconstruction performance. The experiments validated on three datasets demonstrate the effectiveness of HP-ALF and its superiority to the comparative methods.

Pediatric Outpatient Noncontrast Brain MRI: A Time-Driven Activity-Based Costing Analysis at Three U.S. Hospitals

BACKGROUND. MRI utilization and the use of sedation or anesthesia for MRI have increased in children. Emerging alternative payment models (APMs) require a detailed understanding of the health system costs of performing these examinations. OBJECTIVE. The purpose of this study was to use time-driven activity-based costing (TDABC) to assess health system costs for outpatient noncontrast brain MRI examinations across three children's hospitals. METHODS. Direct costs for outpatient noncontrast brain MRI examinations at three academic free-standing pediatric hospitals were calculated using TDABC. Examinations were categorized as sedated MRI (i.e., sedation or anesthesia), nonsedated MRI, or limited MRI. Process maps were created to describe patient workflows based on input from key personnel and direct observation. Time durations for each process activity were determined; time stamps from retrospective EMR review were used when possible. Capacity cost rates were calculated for resource types within three cost categories (labor, equipment, and space); cost was calculated in a fourth category (supplies). Resources were allocated to each activity, and the cost of each process step was determined by multiplying step-specific capacity costs by the time required for each step. The costs of all steps were summed to yield a base-case total examination cost. Sensitivity analysis for sedated MRI was performed using minimum and maximum time duration inputs for each activity to yield minimum and maximum costs by hospital. RESULTS. The mean base-case cost for a sedated brain MRI examination was $842 (range, $775-924 across hospitals), for a nonsedated brain MRI examination was $262 (range, $240-285), and for a limited brain MRI examination was $135 (range, $127-141). For all examination types, the largest cost category as well as the largest source of difference in cost between hospitals was labor. Sensitivity analysis found that the greatest influence on overall cost at each hospital was the duration of the MRI acquisition. CONCLUSION. The health system cost of performing a sedated MRI examination was substantially greater than that of performing a nonsedated MRI examination. However, the cost of each individual examination type did not vary substantially among hospitals. CLINICAL IMPACT. Health systems operating within APMs can use this comparative cost information for purposes of cost reduction efforts and establishment of bundled prices.

State-of-the-art magnetic resonance imaging sequences for pediatric body imaging

Longer examination time, need for anesthesia in smaller children and the inability of most children to hold their breath are major limitations of MRI in pediatric body imaging. Fortunately, with technical advances, many new and upcoming MRI sequences are overcoming these limitations. Advances in data acquisition and k-space sampling methods have enabled sequences with improved temporal and spatial resolution, and minimal artifacts. Sequences to minimize movement artifacts mainly utilize radial k-space filling, and examples include the stack-of-stars method for T1-weighted imaging and the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER)/BLADE method for T2-weighted imaging. Similarly, the sequences with improved temporal resolution and the ability to obtain multiple phases in a single breath-hold in dynamic imaging mainly use some form of partial k-space filling method. New sequences use a variable combination of data sampling methods like compressed sensing, golden-angle radial k-space filling, parallel imaging and partial k-space filling to achieve free-breathing, faster sequences that could be useful for pediatric abdominal and thoracic imaging. Simultaneous multi-slice method has improved diffusion-weighted imaging (DWI) with reduction in scan time and artifacts. In this review, we provide an overview of data sampling methods like parallel imaging, compressed sensing, radial k-space sampling, partial k-space sampling and simultaneous multi-slice. This is followed by newer available and upcoming sequences for T1-, T2- and DWI based on these other advances. We also discuss the Dixon method and newer approaches to reducing metal artifacts.

Acute Hospital Management of Pediatric Stroke

The field of pediatric stroke has historically been hampered by limited evidence and small patient cohorts. However the landscape of childhood stroke is rapidly changing due in part to increasing awareness of the importance of pediatric stroke and the emergence of dedicated pediatric stroke centers, care pathways, and alert systems. Acute pediatric stroke management hinges on timely diagnosis confirmed by neuroimaging, appropriate consideration of recanalization therapies, implementation of neuroprotective measures, and attention to secondary prevention. Because pediatric stroke is highly heterogenous in etiology, management strategies must be individualized. Determining a child's underlying stroke etiology is essential to appropriately tailoring hyperacute stroke management and determining best approach to secondary prevention. Herein, we review the methods of recognition, diagnosis, management, current knowledge gaps and promising research for pediatric stroke.

Safety challenges related to the use of sedation and general anesthesia in pediatric patients undergoing magnetic resonance imaging examinations

The use of sedation and general anesthesia has facilitated the significant growth of MRI use among children over the last years. While sedation and general anesthesia are considered to be relatively safe, their use poses potential risks in the short term and in the long term. This manuscript reviews the reasons why MRI examinations require sedation and general anesthesia more commonly in the pediatric population, summarizes the safety profile of sedation and general anesthesia, and discusses an amalgam of strategies that can be implemented and can ultimately lead to the optimization of sedation and general anesthesia care within pediatric radiology departments.

Magnetic resonance imaging in children with implants

As access to MRI in pediatrics increases, the radiologist needs to become acquainted with the basic principles of MRI safety. As part of the image acquisition, the static magnetic field, gradient system, and the radiofrequency transmit-receive coil interact with medical and non-medical implants and can result in serious injury. The main stage of risk triage is based on the determination of whether the implant is MRI-safe, conditional, unsafe or unknown. Guiding principles include the strict adherence to manufacturer specifications for MRI-conditional implants and the assumption that an unknown implant is MR-unsafe. In this article we review considerations for common medical implants encountered in pediatrics including ventriculoperitoneal shunts, orthopedic hardware, orthodontic hardware, pacemakers, vascular stents, vagal nerve stimulators and cochlear implants. Finally, we review a set of high-yield considerations, including the non-communicative patient (sedated or non-verbal), susceptibility artifacts from unclear source, and the approach to an unknown implant.

Success of Nonsedated Neuroradiologic MRI in Children 1-7 Years Old

BACKGROUND. MRI use and the need for monitored anesthesia care (MAC) in children have increased. However, MAC is associated with examination delays, increased cost, and safety concerns. OBJECTIVE. The purpose of this study was to evaluate the success rate of nonsedated neuroradiologic MRI studies in children 1-7 years old and to investigate factors associated with success. METHODS. We retrospectively reviewed data from our institutional nonsedated MRI program. Inclusion criteria were outpatient nonsedated MRI referral, age 1-7 years old, and neuroradiologic indication. Exclusion criteria were MRI examinations for ventricular checks and contrast material use. Success was determined by reviewing the clinical MRI report. We recorded patient age and sex, type of MRI examination (brain, spine, craniospinal, head and neck, and brain with MRA), protocol length, presence of child life specialist, video goggle use, and MRI appointment time (routine daytime appointment or evening appointment). We used descriptive statistics to summarize patient demographics and clinical data and logistic regression models to evaluate predictors of success in the entire sample. Subset analyses were performed for children from 1 to < 3 years old and 3 to 7 years old. RESULTS. We analyzed 217 patients who underwent nonsedated MRI examinations (median age, 5.1 years). Overall success rate was 82.0% (n = 178). The success rates were 81.4% (n = 127) for brain, 90.3% (n = 28) for spine, 71.4% (n = 10) for craniospinal, 66.7% (n = 6) for head and neck, and 100% (n = 7) for brain with MRA. Age was significantly associated with success (odds ratio [OR], 1.33; p = .009). In children 1 to < 3 years old, none of the factors analyzed were significant predictors of success (all, p > .48). In children 3-7 years old, protocol duration (OR, 0.96; 95% CI, 0.93-0.99; p = .02) and video goggle use (OR, 6.38; 95% CI, 2.16-18.84; p = .001) were significantly associated with success. CONCLUSION. A multidisciplinary approach with age-appropriate resources enables a high success rate for nonsedated neuroradiologic MRI in children 1-7 years old. CLINICAL IMPACT. Using age as the primary criterion to determine the need for MAC may lead to overuse of these services. Dissemination of information regarding nonsedated MRI practice could reduce the rate of sedated MRI in young children.

Diagnostic equivalency of fast T2 and FLAIR sequences for pediatric brain MRI: a pilot study

BACKGROUND

Faster and motion robust magnetic resonance imaging (MRI) sequences are desirable in pediatric brain MRI as they can help reduce the need for monitored anesthesia care, which is a costly and limited resource that carries medical risks.

OBJECTIVE

To evaluate the diagnostic equivalency of commercially available accelerated motion robust MR sequences relative to standard sequences.

MATERIALS AND METHODS

This was an institutional review board-approved prospective study. Subjects underwent a clinical brain MRI using conventional multiplanar images at 3 Tesla followed by fast axial T2 and FLAIR (fluid-attenuated inversion recovery) sequences optimized for an approximately 50% reduction in acquisition time. Conventional and fast images from each subject were reviewed by two blinded pediatric neuroradiologists. The readers evaluated the presence of 12 findings. Intra-observer agreement was estimated for fast versus conventional sequences. For each set of sequences, interobserver agreement calculations and chi-square tests were used to evaluate differences between fast and conventional acquisitions. An independent third reader reviewed the intra-observer discrepancies and adjudicated them as being more conspicuous on fast sequence, conventional sequence or the equivalent. The readers also were asked to rate motion artifacts with a previously validated score.

RESULTS

Images from 77 children (mean age: 11.3 years) were analyzed. Intra-observer agreement (fast versus conventional) ranged between 89.2% and 92.3%. Interobserver agreement ranged between 86.1% and 88.4%. Interobserver agreement was significantly higher for conventional FLAIR relative to fast FLAIR for small (<5 mm) foci of T2 in the white matter. Otherwise, interobserver agreement was not different between the fast and conventional sequences. For awake subjects, fast sequences had significantly fewer artifacts (P<0.05).

CONCLUSION

Conventional T2 and FLAIR sequences can be optimized to shorten acquisition while maintaining diagnostic equivalency. These faster sequences were also less susceptible to motion artifacts.

MRI Techniques to Decrease Imaging Times in Children

Long acquisition times can limit the use of MRI in pediatric patients, and the use of sedation or general anesthesia is frequently necessary to facilitate diagnostic examinations. The use of sedation or anesthesia has disadvantages including increased cost and imaging time and potential risks to the patient. Reductions in imaging time may decrease or eliminate the need for sedation or general anesthesia. Over the past decade, a number of imaging techniques that can decrease imaging time have become commercially available. These products have been used increasingly in clinical practice and include parallel imaging, simultaneous multisection imaging, radial k-space acquisition, compressed sensing MRI reconstruction, and automated protocol selection software. The underlying concepts, supporting data, current clinical applications, and available products for each of these strategies are reviewed in this article. In addition, emerging techniques that are still under investigation may provide further reductions in imaging time, including artificial intelligence-based reconstruction, gradient-controlled aliasing sampling and reconstruction, three-dimensional MR spectroscopy, and prospective motion correction. The preliminary results for these techniques are also discussed. ^©RSNA, 2020 See discussion on this article by Greer and Vasanawala.

Impact of a fast free-breathing 3-T abdominal MRI protocol on improving scan time and image quality for pediatric patients with tuberous sclerosis complex

BACKGROUND

Magnetic resonance imaging (MRI) of the abdomen can be especially challenging in pediatric patients because of image quality degradation from respiratory motion. Abdominal MR protocols tailored for free-breathing children can potentially improve diagnostic image quality and reduce scan time.

OBJECTIVE

To evaluate the performance of a free-breathing 3-T MRI protocol for renal evaluation in pediatric patients with tuberous sclerosis complex (TSC).

MATERIALS AND METHODS

A single institution, Institutional Review Board-approved, retrospective database query identified pediatric TSC patients who underwent a free-breathing 3-T MR abdominal protocol including radial and respiratory-triggered pulse sequences and who also had a prior abdominal MRI on the same scanner using a traditional MR protocol utilizing signal averaging and Cartesian k-space sampling. Scan times and use of sedation were recorded. MR image quality was compared between the two protocols using a semiquantitative score for overall image quality and sharpness.

RESULTS

Forty abdominal MRI studies in 20 patients were evaluated. The mean scan time of the fast free-breathing protocol was significantly lower (mean: 42.5±9.8 min) compared with the traditional protocol (58.7±11.7 min; P=<0.001). Image sharpness was significantly improved for radial T2-weighted and T1-weighted triggered Dixon and radial T1-weighted fat-suppressed post-contrast images in the free-breathing protocol, while image quality was significantly higher on radial and Dixon T1-weighted sequences.

CONCLUSION

A free-breathing abdominal MR protocol in pediatric TSC patients decreases scan time and improves image quality and should be considered more widely for abdominal MRI in children.

Easing anxiety in preparation for pediatric magnetic resonance imaging: a pilot study using animal-assisted therapy

BACKGROUND

Children undergoing magnetic resonance imaging (MRI) can experience negative emotions both before and during their scan, causing them to move and often necessitating the use of procedural sedation. Several strategies to improve patient compliance have been attempted.

OBJECTIVE

This study was designed to evaluate the effectiveness of a non-pharmacological intervention to reduce anxiety in pediatric patients preparing for MRI using animal-assisted therapy.

MATERIALS AND METHODS

An animal intervention pilot study was performed in patients who agreed in advance to interact with a dog. Patients and caregivers filled out questionnaires, including questions designed to capture changes in patient emotion before and after the intervention. MRI diagnostic quality was compared to age- and gender-matched control groups with and without general anesthesia.

RESULTS

The intervention in 21 patients comparing pre- and post-scan surveys demonstrated a statistically significant improvement in patient anxiety levels (P<0.01). Diagnostic MRI scans were achieved in 19/21 (90%), with no significant difference in exam quality or times compared against control groups. The majority of caregivers and staff members agreed strongly that patients benefited from the therapy dog's presence.

CONCLUSION

The use of animal-assisted therapy in a pilot group in our MRI division resulted in a beneficial effect on patients' emotional status, easing anxiety in preparation for scheduled scans, without impacting MRI quality or duration. Further randomized studies will be needed to demonstrate its significance in reducing sedation rates in children undergoing MRI.